The invention relates to a system for forming and releasing an aqueous peracid solution; a composition for forming and releasing an aqueous peracid solution; a method of sanitizing a surface having a population of microorganisms; and a method for manufacturing an article and composition. The system includes a peracid forming composition provided within a container permeable to the passage of water and aqueous peracid sanitizer solution. The composition can be a peracid forming composition including peracid precursor, peroxygen source, and chemical heater. In addition, the composition can include composite structures which include both peracid precursor and peroxygen source adhered together within a composite structure. The method of sanitizing includes a step of combining the system and/or the composition with water to generate an aqueous peracid sanitizer solution and sanitizing a surface having a population of microorganisms.
Numerous classes of chemical compounds exhibit varying degrees of antimicrobial or biocidal activity. Antimicrobial compositions are particularly needed in the food and beverage industries to clean and sanitize processing facilities such as pipelines, tanks, mixers, etc. and continuously operating homogenization or pasteurization apparatus. Sanitizing compositions have been formulated in the past to combat microbial growth in such facilities. For example, Grosse-Bxc3x6wing et al., U.S. Pat. Nos. 4,051,058 and 4,051,059, teach peracetic acid materials. These peroxy-containing compositions are known for use in the production of microbiocidal agents. One such composition disclosed by Grosse-Bxc3x6wing et al. contains peracetic acid, acetic acid or mixtures of peracetic and acetic acid, hydrogen peroxide, anionic surface active compounds such as sulfonates and sulfates, and water. Wang, U.S. Pat. No. 4,404,040, teaches a short chain fatty acid sanitizing composition comprising an aliphatic short chain fatty acid, a hydrotrope solubilizer capable of solubilizing the fatty acid in both the concentrate and use solution, and a hydrotrope compatible acid so that the use solution has a pH in the range of 2.0 to 5.0.
Peracetic acid has been shown to be a good biocide, but only at fairly high concentrations (generally greater than 100 part per million (ppm)). Similarly, peroxyfatty acids have also been shown to be biocidal, but only at high concentrations (greater than 200 ppm), such as in the composition disclosed in European Patent Application No. 233,731. Antimicrobial compositions having low use concentrations (less than 100 ppm) which effectively kill microbes are particularly desirable. Low concentrations minimize use cost, surface corrosion, odor, carryover of biocide into foods and potential toxic effects to the user. Therefore, a continuing need exists to provide such an antimicrobial composition for use in food processing, food service and health care facilities.
Combining a peroxygen source with an acid precursor in forming bleaching compositions or sanitizing compositions has been disclosed in the prior art. The prior art compositions are often formed in an aqueous solution which can be unstable, short lived, corrosive, and difficult to contain due to a need to vent the container containing the aqueous solution. Such compositions require high purity because impurities can catalyze decomposition of the peracid material. Aqueous solutions also require shipping of water which increases costs.
U.S. Pat. No. 5,296,239 to Colery, et al. and U.S. Pat. No. 5,736,497 to Steiner describe aqueous liquid peracid sanitizer formulations. International Publication No. WO 94/11483 describes the use of acylated citrate esters and ethoxylated alcohols as stabilizers. Solid mixtures are also known that generate peracid upon dissolution in aqueous media U.S. Pat. No. 5,505,740 to Kong, et al. describes in situ formation of peracid where the aqueous wash solution is initially raised to a relatively high pH level by introduction of an alkaline agent for enhancing production of the peracid in the aqueous solution, then lowering the pH of the aqueous solution for enhancing bleach performance.
Aqueous peroxygen solutions containing perborates and/or hydrogen peroxide in combination with acids (e.g., boric acid) are often stabilized by the addition of a stabilizing agent. Stabilizing agents described in the prior art include carbazole sulfonates, diphenylamine sulfanates, N-phenylamino naphthalene sulfonates, and diethylenetriamine pentamethylene phosphonic acid. See U.S Pat. No. 5,736,497 to Steiner. This patent additionally describes the stabilization of alkaline hydrogen peroxide solutions by the addition of an organic stannate. U.S. Pat. No. 5,296,239 to Colery et al. describes stabilizing a thickened peracetic composition by adding sequestering agents, free-radical scavengers, and mixtures of sequestering agents and free-radical scavengers.
Techniques for enhancing performance of preformed peracids have been disclosed by a number of prior art references. In particular, U.S. Pat. No. 4,391,725 to Bossu discloses a granular hydrophobic peroxyacid laundry product in the form of a preformed peracid bleach provided within a pouch. An acid additive, indicated as having a pKa of from about 2 to about 7, is combined with the hydrophobic peracid in the pouch in order to aid in release of the peracid from the pouch, thereby enhancing bleach performance. U.S. Pat. No. 4,391,723 to Bacon et al. and U.S. Pat. No. 4,391,724 to Bacon describe the inclusion of boric acid or other acids together with the preformed peracids for improving bleach performance.
A system for forming and releasing an aqueous peracid solution is provided by the invention. The system includes a peracid forming composition and a container for containing the peracid forming composition. The peracid forming composition includes a peracid precursor and a peroxygen source. Preferably, the peracid forming composition includes a chemical heater capable of releasing heat upon hydration. The chemical heater can increase the local temperature within the container by at least about 5xc2x0 C. after the system is placed in water. The local temperature is considered the temperature of the environment within the container. The temperature increase is measured from the ambient temperature of the water in which the system is immersed. The container is permeable to the passage of water and aqueous peracid solution. When the system is immersed in water, water flows into the container, and the peracid forming composition generates peracid which flows out of the container providing an aqueous peracid sanitizer solution having a pH of less than 8.
The peracid precursor is preferably a component which is relatively nonreactive with the peroxygen source under temperature conditions normally found during transportation and storage. Preferred peracid precursors which can be used according to the invention include carboxylic acid anhydrides such as glutaric acid anhydride, succinic acid anhydride, maleic acid anhydride and mixtures thereof. The peroxygen source is preferably a component which remains relatively nonreactive with peracid precursor under temperature conditions normally encountered during the storage and shipment. A preferred peroxygen source includes sodium perborate. It should be appreciated that while the peracid precursor and peroxygen source are characterized as relatively nonreactive toward each other, this is under conditions of storage and transport. The peracid precursor and peroxygen source are preferably very reactive toward each other when combined with water (liquid or vapor). The chemical heater can be any material which is compatible (preferably nonreactive) with the peracid precursor and peroxygen source, and which increases the temperature of the environment within the container when combined with water. Preferably, the chemical heater is included in an amount sufficient to increase the local temperature by at least about 5xc2x0 C. after introducing the system into water. Exemplary chemical heaters include hydratable salts such as salts of inorganic and organic acids, salts of mineral acids, magnesium sulphate, alkaline earth metal salts, and alkali metal salts, and alkaline earth metal oxides.
A composition for forming and releasing an aqueous peracid solution is provided by the invention. The composition can take several forms. One form of the composition includes a mixture of components. For example, the mixture can include about 2 wt % to about 30 wt % of a carboxylic acid anhydride, about 2 wt % to about 30 wt % of a peroxygen source, and about 10 wt % to about 60 wt % of a chemical heater capable of releasing heat upon hydration. Another form of the composition includes a composite structure which can take the form of granules, blocks, tablets, and the like. The composite structure includes peracid precursor and peroxygen source adhered together within the composite structure. A binder holds the peracid precursor and peroxygen source together within each composite structure. The peracid precursor can function as the binder for holding the peracid precursor and peroxygen source together within the composite structure. The binder can include other components such as alcohol ethoxylates and polymers (homopolymers and/or copolymers) of ethylene oxide and/or propylene oxide. The composite structure can additionally include a chemical heater, an acid catalyst, viscosity modifier, a moisture barrier, and combinations thereof.
The composition can be referred to as a peracid forming composition because it includes peracid forming components which react, in the presence of water, to generate an aqueous peracid solution. The composite structure and/or the mixture of peracid forming components can be provided within the container permeable to the passage of water and aqueous peracid solution. It is expected, however, the composite structure will be used without a permeable container. That is, the composite structure will be applied to a wetted surface and the peracid solution will form on the wetted surface. In contrast, it is expected that the mixture of peracid forming components will generally be used to provide a quantity of aqueous peracid solution which can then be used for various applications.
Methods of sanitizing a surface having a population of microorganisms is provided by the present invention. The method includes a step of combining the system for forming and releasing an aqueous peracid sanitizer solution with water, or combining the composite structure for forming and releasing an aqueous peracid sanitizer solution with water. The system can be used for generating a volume of aqueous peracid sanitizer solution. This solution can be provided, for example, in a bucket or container. The sanitizer solution is particularly useful for use in hard surface disinfection, potable water disinfection, fruit/veggie sanitizing rinse, medical instrument sanitization, and kitchen sanitization. The composite structure can be used by scattering the composite granules on a wet surface which is to be treated. The aqueous peracid solution is then generated on the surface. The composite structure can preferably be used in various applications including biohazard cleanup, carpet sanitization, floor sanitization, and ostomy deodorization.
Methods for manufacturing a system for forming and releasing an aqueous peracid solution and for manufacturing composite structures for forming and releasing an aqueous peracid solution are provided by the invention. The methods for manufacturing a system for forming, and releasing an aqueous peracid solution can include the steps of providing a peracid forming composition within a container, and providing a moisture barrier envelope around the peracid forming composition within the container. The moisture barrier envelope is provided for reducing contact of the peracid forming composition with liquid or vapor water. The methods for manufacturing composite structures for forming and releasing an aqueous peracid solution can include a step of adhering peracid precursor and peroxygen source together to provide a composite structure including both peracid precursor and peroxygen source adhered together. The composite structure can include a chemical heater and/or acid catalyst as part of the structure. In general, the adhesion of the components together will be accomplished with a binder. The peracid precursor can function as the binder. In addition, a moisture barrier coating can be provided around the composite structures, and/or around the peracid precursor component, the peroxygen source components, or both components separately.